%0 Review article
%T Major decline in fires in coniferous forests – reconstructing the phenomenon and seeking for the cause
%A Wallenius, Tuomo
%D 2011
%J Silva Fennica
%V 45
%N 1
%R doi:10.14214/sf.36
%U https://silvafennica.fi/article/36
%X Steep decline in forest fires about a century ago occurred in coniferous  forests over large areas in North America and Fennoscandia. This poorly  understood phenomenon has been explained by different factors in  different regions. The objective of this study is to evaluate the  validity of the four most commonly suggested causes of the decrease in  forest fires: fire fighting, over-grazing, climate change and human  influence. I compiled the available dendrochronological data and  estimated the annually burned proportions of Pinus-dominated forests in  four subcontinental regions during the past 500 years. These data were  compared to the development of fire suppression, grazing pressure,  climate and human livelihoods. The annually burned proportions declined  over 90% in all studied regions. In three out of the four regions fires  decreased decades before fire suppression began. Available drought data  are annually well correlated with fires but could not explain the  decrease of the level in annually burned areas. A rapid increase in the  number of livestock occurred at the same time with the decrease in fires  in the Western US but not in Fennoscandia. Hence, fire suppression in  Central Fennoscandia and over-grazing in the Western US may have locally  contributed to the reduction of burned areas. More general explanation  is offered by human influence hypothesis: the majority of the past  forest fires were probably caused by humans and the decrease in the  annually burned areas was because of a decrease in human caused fires.  This is in accordance with the old written records and forest fire  statistics. The decrease in annually burned areas, both in Fennoscandia  and the United States coincides with an economic and cultural transition  from traditional livelihoods that are associated with high fire use to  modern agriculture and forestry.